1. Field of the Invention
The present invention relates to a liquid crystal display (LCD), and more particularly, to a liquid crystal display panel and a method for fabricating the same by a liquid crystal dropping method.
2. Discussion of the Related Art
A thin flat panel display tends to have a thickness of no more than a few centimeters. Particularly, a liquid crystal display (LCD) has a wide scope of applications, such as notebook computers, computer monitors, gauge monitors for space crafts and air crafts, and the like.
In general, the LCD is provided with a lower substrate having thin film transistors and pixel electrodes formed thereon, an upper substrate opposite to the lower substrate having a black matrix (BM), a color filter layer, and a common electrode, which are formed thereon, and a liquid crystal layer between the two substrates, for driving the liquid crystal by the electric field generated by the power supply applied to the pixel electrodes and the common electrode between the substrates, to regulate the transmittivity of the liquid crystal, thereby displaying a picture on the display screen.
In the foregoing LCD, a vacuum injection method has been used for forming the liquid crystal layer between the lower substrate and the upper substrate. In such a method, after the lower substrate and the upper substrate are attached to each other, a liquid crystal is injected between the two substrates by using capillary phenomenon and a pressure difference. However, the vacuum injection method takes much time to inject the liquid crystal between the substrates. As a result, productivity is much reduced as the substrate becomes large.
Consequently, a method called a liquid crystal dropping method is suggested for solving such a problem. A method for fabricating an LCD panel by using a related art liquid crystal dropping method will be explained with reference to the attached drawings.
FIGS. 1A to 1D illustrate expanded perspective views showing a method for fabricating an LCD panel by using a related art liquid crystal dropping method.
Referring to FIG. 1A, a lower substrate 1 and an upper substrate 3 are prepared for the process. A plurality of gate lines and data lines (both not shown) are formed on the lower substrate 1 to cross each other defining pixel regions. A thin film transistor is formed at every crossing point of the gate lines and the data lines. A pixel electrode is formed at every pixel region connected to the thin film transistor.
A black matrix is formed on the upper substrate 3 for shielding a light leakage from the gate lines, the data lines, and the thin film transistor regions. A color filter layer of red, green, and blue is formed thereon. A common electrode is formed thereon in this order. An orientation film is formed on both of the lower substrate 1 and the upper substrate 3 for an initial orientation of the liquid crystal.
In FIG. 1B, a main sealant 7 and a dummy sealant 8 are coated on the lower substrate 1, and a plurality of liquid crystal droplets 5 are positioned thereon, to form a liquid crystal layer. Then, spacers (not shown) are spread on the upper substrate 3 for maintaining a cell gap.
In the liquid crystal dropping method, the liquid crystal layer is already placed between the attached substrates before setting a sealant. Accordingly, if a thermo-hardening sealant is used to bond the substrates, it may flow and contaminate the liquid crystal during the heating process. Thus, a UV sealant has to be used as a sealant to avoid such a problem.
Referring to FIG. 1C, the lower substrate 1 and the upper substrate 3 are attached to each other. As shown in FIG. 1D, a UV ray is irradiated by using a UV irradiating device 9 to harden the sealant 7 (shown in FIG. 1B), thereby bonding the lower substrate and the upper substrate 3.
However, the sealant 7 is not hardened until the UV ray is irradiated thereon. Therefore, the sealant 7 may be deformed when the external force is applied onto the lower substrate 1 and the upper substrate 2 during the process of bonding the lower substrate 1 and the upper substrate 2.